Animation node instancing an object with children
Since an object doesn't store reference to its children, I would advise to use a collection for this, and create an empty as a collection instancer. Be aware that every instanced collection will have the same animation as the first one:

For example, I have this collection with a cube and a Suzanne children.



Create empties as instance collections :



Loop over them and change their position :



Increase the number of instances :